You have no signal although you are sure, that there should be one? Just go to:
Settings and turn Airplane Mode on
Afterwards wait a short period of time and turn Airplane Mode off. Your phone starts searching for the missing signal, once again. If it still doesn’t find a signal, try a restart.
Sometimes your device will need a restart, for example if some apps don’t open or constantly remain frozen.
Restart iPad: Press and hold the On⁄Off button until the red slider appears. Slide your finger across the slider to turn off iPad. To turn iPad back on, press and hold the On⁄Off button until the Apple logo appears.
If you can’t turn off iPad or if the problem continues you may need to reset your iPad.
A reset should be done only if turning iPad off and on doesn’t resolve the problem. Be sure to have a current backup.
Reset iPad: Hold down the On⁄Off button and the Home button at the same time for at least 10 seconds, until the Apple logo appears.
When the iPad software has been restored, you can either set it up as a new iPad, or restore your music, videos, app data, and other content from a backup.
After you restore from a backup, previous data is no longer accessible through the iPad user interface, but it isn’t erased from iPad.
iCloud stores your photos, apps, contacts, calendars, and more, and wirelessly pushes it to your iOS devices and computers, automatically keeping everything up to date.
iCloud features include:
With iCloud, you get a free email account and 5 GB of storage for your mail, documents, and backup. Your purchased music, apps, TV shows, and books, as well as your Photo Stream, don’t count against your free space.
Note: iCloud is not available in all areas, and iCloud features may vary by area.
Choose info to store in iCloud: Go to Settings > iCloud.
Turn Automatic Downloads on or off: Go to Settings > Store.
View and download previous iTunes Store purchases: Go to iTunes, then tap Purchased
View and download previous App Store purchases: Go to App Store, tap Updates, then tap Purchased.
View and download previous iBooksstore purchases: Go to iBooks, tap Store, then tap Purchased.
Turn Photo Stream on or off: Go to Settings > iCloud.
Find your iPad: Visit www.icloud.com. Important: On your iPad, Find My iPad must be turned on in Settings > iCloud in order for Find My iPad features to be available.
Purchase additional iCloud storage: Go to Settings > iCloud > Storage and Backup, then tap Manage Storage. For information about purchasing iCloud storage, see help.apple.com/icloud.